RADIOACTIVE ISOTOPES 305 January, 1958 During a surgical operation at Utrecht, Holland, a child vomited so that a radium needle was lost. It was found in the garden. The house and garden had to be decon- taminated. May, 1958 At Berlin insufficient precautions were taken in the use of radiolsotopes with consequent contamination of the premises. June, 1958 An error on the part of a workman when dealing with enriched uranium at Oak Ridge, U.S.A., caused injury to eight people, five of whom had bone disease. January, 1960 A bottle containing a solution of plutonium alloy broke at Los Alamos, U.S.A. The decon- tamination of the room occupied about a week. METHOBS OF PRODUCTION Reactors. The majority of the 800 or so radio isotopes known are made by exposure of non-radioactive elements to radio- activity in nuclear reactors. A great deal of radiolsotope pro- duction is undertaken in the reactors at Harwell. Cyclotron. Some radioisotopes can be produced by means of the particle accelerator. Cyclotrons and similar devices are not infrequently found in the research laboratories of universities. Others are owned by industrialists for research and radioisotope production. Certain radioisotopes can more conveniently be produced In this way while, for some of them, this means is at present the only method of producing them. Radioactive Waste. A third source of radioisotopes and one likely to be expanded considerably alongside the nuclear power programme of this country is the radioactive waste obtained from reactors from which radioisotopes can be recovered In the course of re-processing the waste. One of the embarrassments occasioned by the use of nuclear reactors is the Increasing volume of this waste and the problems posed by Its disposal. After use in a reactor the fuel (usually uranium) not only acquires Impurities but undergoes physical and chemical changes with resultant radioactivity. Eventually, the fuel has to be removed from the reactor In order that It may be re-processed for further use. The radioactive waste products are then removed by complicated chemical separation processes. Research is now RCD)